We propose to study the coordination of muscle contraction using a genetic approach in the nematode, Caenorhabditis elegans. One set of genes thought to be involved in the regulation of body wall muscle contraction is represented by the genes unc-93, sup-9, sup-lO, sup-11 and sup-18. Certain gain-of-function alleles of the first three of these genes confer a characteristic paralyzed phenotype termed "rubberband". Muscle structure of these animals appears fully normal, suggesting that these genes are involved in the regulation of muscle contraction rather than in the contractile apparatus itself. We have isolated novel suppressors of the rubberband phenotype conferred by an allele of unc-93. We intend to fully characterize these suppressor alleles, genetically map their position in the genome and locate a genomic clone corresponding to the suppressor gene. We will also undertake a complete molecular characterization of mutant alleles currently in our possession. Approaches for isolating addition mutant alleles, both null and non-null alleles, are described.